SINK OR FLOAT
COPY CHART Make prediction
OBJECT
Empty plastic jar
Water filled plastic jar
Rubber stopper
wood
Metal clip
cork
Pen cap
PREDICT S or F
ACTUAL S or F
DEMONSTRATION
Drop a coin. An aluminum quarter into a beaker filled
with water
Drop an aluminum foil ball into a beaker of water
Both are metallic and have a density of 2.7g/ml
PREDICT WHAT WILL HAPPEN?
WHY DO SOME OBJECTS FLOAT AND SOME SINK?
INSTRUCTIONAL OBJECTIVES
1. DEFINE BUOYANCY (and Archimedes Principal)
2.
Explain why some objects sink while others float
3. Explain what happened to the titanic when it hit the iceberg
WHY DO SOME OBJECTS FLOAT WHILE OTHER
OBJECTS SINK?
The coin sinks because it weighs more than the water it displaces. The aluminum foil
ball floats because there is air trapped inside the folds. Air weighs less than
water; so the ball weighs less than the water it displaces
TITANIC STORY
GUESS THE AIM??????
AIM: HOW DID THE TITANIC SINK?
SOLVE THE PHYSICS/ALGEBRA equation on the worksheet
1. How much does the object weigh in air?___
2. How much does it weigh in water?______
3. What is the apparent loss of weight in water?_____
ARCHIMEDES
GREEK SCIENTIST
BUOYANCY
•
Archimedes the Greek scientist discovered that –floating objects are supported by a
force called BUOYANCY.
•
ARCHIMEDES PRINCIPAL
•
1. the buoyant force on any object is equal to the weight of the liquid the object
displaces
•
2. an object immersed in a liquid appears to lose weight, and the apparent weight loss
is equal to the weight of the liquid displaced
BUOYANCY OF PERSON IN OCEAN
HOW DID ARCHIMEDES PRINCIPAL EXPLAIN HOW
THE TITANIC SANK?
TAKE A FEW MINUTES AND WRITE SEVERAL
SENTENCES EXPLAINING THIS PRINCIPAL
KEY WORD: BUOYANCY
USING ARCHIMEDES PRINCIPAL EXPLAIN HOW
THE TITANIC SANK?
A steel ship floats because it is constructed to have
many air compartments. The Titanic sank because
its air filled compartments(bulkheads) filled with
water after the collision with an iceberg. The added
weight of the water plus the weight of the ship
became greater than the buoyant force supporting
the ship, thus causing it to sink rapidly.
SUMMARY
An object sinks when the weight of the object is
greater than the buoyant force that supports
the object. An object floats when it weighs
less than the water supporting it.
SUMMARY QUIZ
1. TRUE OR FALSE CORRECT FOR FULL CREDIT
If a boat weighs 1000 pounds and the buoyant force supporting is 800 newtons.
The boat will sink.
2. Explain why the titanic sank scientifically?
3.
why does a metal anchor sink to the ocean bottom?